Method and apparatus for forming a shadow mask frame

ABSTRACT

A METHOD AND APPARATUS FOR FORMING A SHADOW MASK FRAME HAVING A DISH-SHAPED WALL POSITIONED OBLIQUELY WITH RESPECT TO THE LONGITUDINAL AXIS OF THE FRAME. THE SHADOW MASK FRAME IS FORMED BY APPLYING COLUMNAR FORCE TO A WALL OF A WORKPIECE IN A DIRECTION PARALLEL TO THE LONGITUDINAL AXIS CAUSING COMPLETE PLASTIC DEFORMATION OF THE FRAME. SIMULTANEOUS TO THE STEP OF APPLYING FORCE, A SECOND WALL OF THE WORKPIECE IS CONTAINED WITHIN A PAIR OF CONCAVE CONVEX COMPLEMENTARY SIZED DIES SO AS TO FORM A DISH-SHAPED CONFIGURATION. THE APPARATUS HAS A TOP DIE WITH STUFFING LEDGE MOVABLE TOWARD A BOTTOM DIE WITH A CONVEX PORTION. THE STUFFING LEDGE FORCES THE WORKPIECE BETWEEN THE COMPLEMENTARY SIZED DIES THEREBY FORMING THE DISH SHAPE. SIMULTANEOUSLY, A PUNCH PASSES THROUGH THE WORKPIECE AND IS HELD THEREIN DURING THE PLASTIC DEFORMATION TO ACCURATELY SIZE THE OPENING OF THE SHADOW MASK FRAME.

Feb. 13, 1973 R. E. ROPER 3,715,906

METHOD AND APPARATUS FOR FORMING A SHADOW MASK FRAME Filed March 30, 1971 4 Sheets-Sheet 1 5 INVENTOR.

RAL PH E. ROPE/ Feb. 13, 1973 R E ROPER 3,715,906

IN VEN TOR. RALPH E. ROPER [l/mdmaf, MM, M Wu AT TURN EYS Filed March 30, 1971 R. E. ROPER 3,715,906

METHOD AND APPARATUS FOR FORMING A SHADOW MASK FRAME 4 Sheets-Sheet 3 RALPH E; ROPE wm,u/M,M g e I ATTORNEYS Feb. 13, 1973 R. E. ROPER 3,715,906

METHOD AND APPARATUS FOR FORMING A SHADOW MASK FRAME Filed March 30, 1971 q Sheets-Sheet 4 RALPH E. POPE zammzwmqm ,5 W

ATTORNEYS [N VEN TOR.

United States Patent 3,715,906 METHOD AND APPARATUS FOR FORMING A' SHADOW MASK FRAME Ralph E. Roper, Indianapolis, Ind., assignor to Wallace Expanding Machines, Inc., Indianapolis, Ind. Filed Mar. 30, 1971, Ser. No. 129,483 Int. Cl. B21d 19/08 U.S. Cl. 72-354 11 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for forming a shadow mask frame having a dish-shaped wall positioned obliquely with respect to the longitudinal axis of the frame. The shadow mask frame is formed by applying columnar force to a Wall of a workpiece in a direction parallel to the longitudinal axis causing complete plastic deformation of the frame. Simultaneous to the step of applying force, a second wall of the workpiece is contained within a pair of concave convex complementary sized dies so as to form a dish-shaped configuration. The apparatus has a top die with stufiing ledge movable toward a bottom die with a convex portion. The stufiing ledge forces the workpiece between the complementary sized dies thereby forming the dish shape. Simultaneously, a punch passes through the workpiece and is held therein during the plastic deformation to accurately size the opening of the shadow mask frame.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a method and apparatus for producing shadow mask frames for television receivers and the like.

Description of the prior art A representable sample of the prior art is disclosed in the following US. patents:

2,120,595 issued to Ash 2,715,377 issued to Gary 2,952,899 issued to Glavan 3,295,347 issued to Fuessle 3,442,110 issued to Walton As described in my copending application listed in the Description of the Preferred Embodiment in this specification, the shadow mask frame of a television receiver must be very accurately positioned so as to insure the proper operation of the receiver. Since the shadow mask frames are typically drawn, all stresses within the frame must be relieved in order to prevent subsequent distortion of the frame. It is desirable to provide a shadow mask frame having a spherical or dish-shaped wall so as to more accurately receive the shadow mask of the receiver. The method and apparatus disclosed herein may be utilized to provide such a shadow mask frame.

SUMMARY OF THE INVENTION The present invention is a method of producing a shadow mask frame comprising the steps of: forming a closed annular workpiece having a first wall and a second wall integrally joined and extending together circumferentially around the longitudinal axis extending through said workpiece; exerting columnar force axially of said frame against said first wall to cause plastic deformation of said workpiece; supporting said first wall with a first pair of parallel spaced apart surfaces to prevent buckling of said first wall; containing said second wall during said plastic deformation with a pair of complementary concave and convex dies; forcing a punch through said workpiece; and,

3,715,906 Patented Feb. 13, 1973 holding said punch in said workpiece during said plastic deformation to final size the opening of said frame.

The present invention also is an apparatus for forming a shadow mask frame comprising: a male die having an annular configured stufiing ledge and ridge, said ridge having a first surface parallel with and extending around the longitudinal axis of said die, said ridge having a second surface positioned obliquely to and extending around said axis with said second surface having a first pair of equally radiused concave recesses and a second pair of equally radiused concave recesses; a female die receiving said male die and having a third surface parallel with and spaced from said first surface and extending around said first die, said female die having a second ridge with convex portions complementary sized to said first and second pair of concave recesses; and, press means operable to move along said axis to force said first die and said second die together.

It is an object of the present invention to provide a method for producing a shadow mask frame having a spherical dish-shaped wall.

It is an additional object of the present invention to provide an apparatus for forming a shadow mask frame having a spherical dish-shaped wall.

Related objects and advantages of the present invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view of a shadow mask frame prior to being reformed by the method and apparatus of the present invention.

FIG. 2 is a fragmentary cross-sectional view taken along a line and viewed in the direction of arrows 2-2 of FIG. 1.

FIG. 3 is the same view as FIG. 1 only showing the shadow mask frame after the frame has been reformed according to the present invention.

FIG. 4 is a cross-sectional view taken along a line and viewed in the direction of arrows 4-4 of FIG. 3.

FIG. 5 is a cross-sectional view taken along a line and viewed in the direction of the arrows 5-5 of FIG. 3.

FIG. 6 is a perspective view of the apparatus incorporating the present invention with portions of the shadow mask frame and apparatus being fragmented and/ or sectioned.

FIG. 7 is a cross-sectional view of the apparatus of FIG. 6 with the dies of the apparatus being in the open position.

FIG. 8 is the same view as FIG. 7 only with the dies shown in the closed position and with only a portion of the apparatus being shown.

FIG. 9 is an enlarged fragmentary view of the dies of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawing and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The invention disclosed herein provides a method and apparatus for producing and reforming shadow mask frames. I hereby incorporate by reference my copending U.S. patent application entitled Process for Manufacture of Shadow Mask Frames, Ser. No. 750,856, filed Aug.

7, 1968 issuing as U.S. Pat. No. 3,584,366 with the issue date being June 15, 1971.

Referring now to FIG. 1, there is shown a shadow mask frame 15. Frame 15 is the workpiece for forming the frame of FIG. 3. The workpiece shown in FIG. 1 may be produced from a strip of metal which is then rolled to form a right angle which extends the length of the strip. The ends of the strip may then be welded together in the form of a hoop and the hoop then being expanded to the general rectangular shape shown in FIG. 1. Frame 15 has a first wall 16 and a second wall 17 arranged perpendicularly being integrally joined together and extending circumferentially around a longitudinal axis 18 which extends through the center of frame opening 19. The cross-sectional view of the frame in FIG. 2 illustrates the perpendicularity of wall 16 with respect to wall 17. It is also to be noted that wall 16 has a longer length than wall 17. The method and apparatus disclosed herein utilize frame 15 as a workpiece transforming the workpiece into the shadow mask frame 20 shown in FIGS. 3 through 5. Frame 20 has a first wall 21 and a second wall 22 which are integrally joined together and which extend around the longitudinal axis 23 extending through the centerof opening 24. By comparing frame 15 with frame 20, it is apparent that wall 21 has a relatively shorter length when compared to wall 16 and wall 22 has a relatively longer length when compared with wall 17. Workpiece 15 is reshaped so as to form a concave recess in wall 22 along each side of the frame. For example, side 27 has a concave recess defined by radius R1 which is identical to a concave recess formed in side 28 also being defined by a radius of equal length to R1. FIG. shows that a concave portion defined by radius R2 is formed in side 26- An identically shaped and configured concave recess Of a radius equal to the length of radius R2 is formed in side 25. In addition, it is to be noted that wall 22 is positioned obliquely with respect to longitudinal axis 23. That is, wall 22 at sides 25, 26, 27 and 28 intersects the longitudinal axis at an oblique angle. Wall 21 extends around the longitudinal axis and is parallel therewith.

The apparatus incorporating the present invention will now be described. FIG. 7 is a fragmentary cross-sectional view of the apparatus incorporating the present invention showing the dies in the open position. FIGS. 6, 8 and 9 illustrate a portion of the apparatus with the dies shown in the closed position. Apparatus 40 (FIG. 7) has a bottom support plate 41 with a top press plate 43 movably mounted thereto. Rods 42 are mounted to plate 41 and extend upward into bearing collars 44 secured to the corners of plate 43. A press means 45 applies force to plate 43 so as to move the plate to and from plate 41. A male die 46 is secured to the bottom of plate 43 by suitable fastening means. Die 46 has an annular configured stuffing ledge 47 and ridge 49 extending around the longitudinal axis 58 of the die. Ridge 49 is formed by a first surface 48 parallel with and extending around axis 8 and a second surface 50 which is positioned obliquely to and extending around axis 58. A female die 55 secured to plate 41 by suitable fastening means is positioned within cavity 61 of plate 41. Wedge blocks 55' are positioned between die 55 and plate 41 to prevent relative motion therebetween. The female die receives male die 46 as plate 43 is forced towards plate 41. Die 55 has a vertical surface 56 which is parallel with and spaced from surfaces 57 and 48. Surface 56 is parallel with axis 58 and extends completely around die 46 when the two dies are mated together as shown in FIG. 6. As previously mentioned, wall 22 (FIG. 3) is obliquely positioned with respect to wall 21 and has two equally radiused bowed portions in the opposite sides 27 and 28 and two other equally radiused bowed portions in the remaining two opposite sides 25 and 26. Thus, die 46 has a pair of concave surfaces 50 (FIG. 7) positioned on the opposite sides of axis 58 for forming the recesses in sides 27 and 28 (FIG. 3) of wall 22. Surfaces 50 extend downward to the dash position shown as 50 (FIG. 9) so as to form the concave configuration. Likewise, surface 50 extends on the remaining two opposite sides to form a second pair of concave recesses so as to allow forming the concave recesses in sides 25 and 26 of wall 22 (FIG. 3). Ridge 59 (FIG. 9) of die 55 is formed by vertical surface 51 and convex surface 62 which extends to location 50' so as to be complementary to and fit within concave surface 50. Surfaces 50 and 62 are spaced apart when the dies are closed so as to form four pairs of surfaces, each pair receiving wall 22 on one of the four frame sides 25, 26, 27 and 28 (FIG. 3).

To form frame 20, dies 46 and 55 are moved apart and frame 15 is inserted therebetween with walls 16 and 17 of the frame being positioned adjacent respectively surfaces 56 and 62. Die 46 is then moved toward die 55 with stufiing ledge 47 abutting the free edge of wall 16. Sufficient force is applied by the stuffing ledge so as to regenerate frame 15 through complete plastic deformation to the shape of frame 20. The length of Wall 16 is decreased while the length of wall 17 is increased. Surfaces 56 and 48 define an annular cavity which has a length n the direction of axis 58 less than the length of wall 16. Likewise, surfaces 50 and 62 define an annular cavity having a length in a direction toward axis 58 greater than the length of wall 17. Thus, a portion of wall 16 is stuffed between surfaces 50 and 62 so as to increase the length f wall 17. Surfaces 56 and 48 are spaced apart a constant distance as are surfaces 50 and 62. Thus, Walls 21 and 2-2 of frame 20 each have a constant thickness. Stopping rods are mounted to plate 41 having upper surfaces 81 for abutting plate 43 thereby limiting the downward travel of die 46 (FIG. 8).

A punch 52 is integrally connected to male die 46 immediately inward and extending along with surface 50 around axis 58. A cavity is provided in plate 41 and die 55 for receiving punch 52. Mounted within the cavity of bottom plate 41 is a stripper pad 64 which is biased toward die 46 by springs 65. Holes are provided in plate 41 and pad 64 for receiving the opposite ends of springs 65. Fitted rods 66 are fixedly mounted to plate 41 with the heads of rods 66 being received by counterbores 67 provided i pad 64. Thus, as die 46 moves into die 55, the bottom 54 of die 46 will force pad 64 against plate 41 with the heads of rods 66 being received by cavity 53 of die 46. As die 46 moves away from die 55, springs 65 will force upward pad 64 until the heads of rods 66 bottom within counterbores 67. Eventually, the top edge of pad 64 will abut the most inward portion of frame 20 thereby forcing the frame from die 55. Best results have been obtained by providing that the most inward portion of wall 22 f frame 20 projects approximately 0.020 inch inwardly of surface 51 of pad 64. Thus, this 0.020 inch protrusion will contact pad 64 thereby forcing the entire frame from the female die.

A stripper ring 68 fixedly mounted to headed members 69 is biased away from plate 43 by springs 71. Holes are provided in stripper ring 68 and plate 43 for receiving the opposite ends of springs 71. Counterbores 70 are provided in plate 43 to receive the heads of rods 69. In many cases, frame 20 will become temporarily fixed with respect to die 46 as die 46 is withdrawn from die 55. Shoulder 72 projects between surfaces 56 and 57 thereby abutting frame 20 and forcing the frame from die 46 asdie 46 is moved upwardly.

The first step of the method for producing frame 20 is to form a closed annular workpiece having a first wall and a second wall integrally joined and extending together circumferentially around the longitudinal axis extending throuugh the workpiece. Such an annular workpiece is shown as frame 15 in FIG. 1; however, it is understood that a different configured workpiece may be utilized other than the exact frame shown in FIG. 1. Columnar force is then exerted axially of the workpiece against the edge of the workpiece wall so as to cause plastic deformation of the workpiece. Simultaneously, the wall is supported by the pair of parallel spaced apart surfaces 56 and 48' (FIG. 7) so as to prevent buckling of the wall. The resulting second wall is then contained during the plastic deformation by the pair of complementary concave and convex die previously explained. Punch 52 is forced through opening 19 of the workpiece and held therein during the plastic deformation in order to final size opening 24 of the finished frame 20. Due to the concave and convex dies, the columnar force is first applied to the edge of Wall 16 at the four corners or frame 15. As piece bows, die 46 will gradually contact the entire edge of wall 16 thereby providing a permanent bow in wall 16 in the direction of axis 23. Sufficient force is applied to the edge of wall 16 so as to decrease the length of wall 16 during the plastic deformation and to increase the length of wall 17. The steps of exerting columnar force and containing the second wall are such so as to cooperatively position wall 17 obliquely to axis 23 and to cooperatively form two equal radiused bowed portions in two opposite sides of wall 22 and two other equal radiused bowed portions in the remaining two opposite sides of wall 22. Wall 22 is thus formed into a rectangular dish-shaped configuration.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

The invention claimed is: 1. A method of producing a shadow mask frame comprising the steps of:

forming a closed annular workpiece with four corners and having a first wall and a second wall integrally joined and extending together circumferentially around the longitudinal axis extending through said workpiece; exerting columnar force axially of said frame against said first wall to cause plastic deformation of said workpiece, said exerting step includes the substeps of:

applying columnar force to an edge of said first wall first only at said four corners of said workpiece;

increasing said columnar force gradually to said edge of all of said first wall causing said first wall to bow in the direction of said axis; and,

increasing said columnar force applied to said first Wall to decrease the length of said first wall in the direction of said axis and increase the length of said second wall;

supporting said first wall with a first pair of parallel spaced apart surfaces to prevent buckling of said first wall;

containing said second wall during said plastic deformation with a pair of complementary concave and convex dies;

forcing a punch through said workpiece; and,

holding said punch in said workpiece during said plastic deformation to final size the opening of said frame.

2. The method of claim 1 wherein:

said first pair of surfaces are parallel to said axis; and,

said exerting step and said containing step cooperatively position said second wall obliquely to said axis in a general rectangular configuration and cooperatively form two equal radiused bowed portions in two opposite sides of said second wall and two other equal radiused bowed portions in the remaining two opposite sides of said second wall.

3. The method of claim 2 wherein:

said workpiece is formed from a strip of metal which has ends joined together, said strip forms a hoop which is expanded to a rectangular shape; and,

said forming step includes positioning said first wall perpendicularly to said second wall prior to said exerting step.

4. An apparatus for forming a shadow mask frame comprising:

a male die having an annular configured stuffing ledge and ridge, said ridge having a first surface parallel with and extending around the longitudinal axis of said die, said ridge having a second surface positioned obliquely to and extending around said axis with said second surface having a first pair of equally radiused concave recesses and a second pair of equally radiused concave recesses;

a female die receiving said male die and having a third surface parallel with and spaced from said first surface and extending around said male die, said female die having a second ridge with convex portions com plementary sized to said first and second pair of concave recesses; and,

press means operable to move along said axis to force said first die and said second die together.

5. The apparatus of claim 4 and further comprising:

a stripper pad adjacent said female die and having springs therebetween which bias said pad toward said male die movably forcing said workpiece from said female die as said male die and female die separate, said pad having a surface aligned with said first surface; and wherein:

said male die has a punch mounted thereto immediately inward of, and extending along with said second surface around said axis, said male die contacting said stripper pad and compressing said springs when said male die and said female die are closed; and,

said female die has a cavity positioned inward of said second surface receiving said punch and said stripper pad.

6. The apparatus of claim 5 and further comprising:

a stripper ring mounted adjacent said male die and spring biased toward said female die movably forcing said workpiece from said rnale die as said male die and female die separate, said stripper ring surrounding said male die and having a surface aligned with said third surface; and,

support means receiving said female die and preventing movement thereof as said press means moves said male die along said axis.

7. The apparatus of claim 6 wherein:

said stripper ring has a ledge projecting between said first surface and said third surface.

8. The apparatus of claim 4 wherein:

said male and female dies are movable apart to receive an annular workpiece which has a first wall with length in the direction of said axis, said workpiece has a second wall with length;

said first and third surface form an annular cavity with length in the direction of said axis less than the length of said first wall of said workpiece; and

said concave recesses and said convex portions form an annular cavity with length greater than the length of said second wall of said workpiece.

9. The apparatus of claim 8 wherein:

said stuffing ledge abuts said workpiece causing complete plastic deformation of said workpiece; and,

said stripper ring is suspendedly mounted to said press means.

10. A method of reforming a shadow mask frame having first and second generally perpendicular walls comprising the steps of:

applying force to the edge of said first wall and in a direction parallel to said first wall causing plastic deformation of said frame and a decrease in the length of said first wall;

containing said second wall between a convex die and a mating concave die, said force deforming said second wall between said convex die and concave die into a general dish-shaped configuration; and holding a sizing die through said second wall as said frame is being plastically deformed during said applying and containing steps; and wherein: said second Wall is positioned during said containing step obliquely with respect to the longitudinal axis of said frame and is contained so as to form a first pair of equally radiused concave portions and a second pair of equally radiused concave portions therein. 11. The method of claim 10 wherein said first wall and said second wall each have a constant wall thickness subsequent to said force applying step.

References Cited UNITED STATES PATENTS Lemmerz 72-354 Adams et al. 29-15901 Le Jeune 29159.0-1 U Stevenson 72--354 Williams 29'412 U Wilcox 2.9159.1 Le Jeune 72--348 U.S. Cl. X.R. 

